I changed out my Mobi cartridge and set this morning. No issues noted. Ate late breakfast and bolused accordingly. BS has been over 300 all day despite multiple manual corrections (13 units total). The entire day, the pump has shown as much as 7 units on board but no decrease in BS levels.
Finally around 7pm, I changed out the cartridge and set. The cannula was very bent. So I put a new cartridge/set in. My two questions are
when you know your pump says you still have loads of IOB - far more than you needed for the carbs you consumed 8 hours ago - where the heck does the insulin go? It’s clearly not getting into the bloodstream otherwise my numbers would be much lower. (BTW I asked a rep at Tandem this question some weeks ago and he did not know. So I asked him if the value for IOB is valid only as long as the device is not malfunctioning. He said he thought that was correct. I was blown away by this.
once the new cartridge/set were installed, my pump showed the same number of IOB as before - no surprise there. My BS readings are now at 342 with over 4 units of IOB but probably there is no IOB because of the bent cannula. How do I get the pump to “reset” itself to show the accurate amount of IOB?
I know when this happens to me when I take the infusion set off there is usually a noticeable smell of alcohol. I think a lot of it ends up on the skin
I agree with Jim. If I can smell insulin on my fingers if I rub around the adhesive area, I know something has gone wrong even without removing the site.
I don’t think you can reset IOB without restarting the pump. When t:slim errors require a restart, the pump locks up and tells you to call Tandem customer support (in part to record issues for warranty purposes), and they guide you through the restart. I’ve had to restart the t:slim enough over the years that I know how to do it, but I have no idea with the Mobi.
With that in mind… I don’t restart when my infusion set goes wrong. I ignore the IOB, give myself a syringe injection to correct, change the site, and just wait until the IOB works itself out over the next hours. Sometimes the syringe correction ends up being the same as the IOB actually, and it all works out.
If you’re worried about the wrong IOB messing up Control IQ, it might be best to turn off CIQ temporarily. Then set an alarm to remind you to turn it back on later.
Not a Tandem user, so I don’t know, but wondering - if you change your insulin duration setting to the shortest duration, that would seem to flush out the IOB number on your pump faster, right? Isn’t there a 2 hour setting for duration?
So for example, if your duration time is normally set for 5 hours, and you change it to 2 hours, you get rid of the IOB 3 hours faster. And then after your real duration time of 5 hours has passed, you can set it back to 5 hours on your pump, and everything should be back to normal.
Again, I don’t know, just suggesting it as a possible thing to try.
That could be done if not using Control IQ. Annoyingly, Control IQ only allows a 5-hour IOB.
Sidenote – IOB with Control IQ continues to befuddle me all around. Here’s a Tandem explainer: Insulin on Board (IOB) “IOB now includes all basal insulin delivered above or below the programmed Basal Rate, not just insulin from bolus deliveries.” No wonder I’ve been confused…
I’d like a step between manual pumping and CIQ. CIQ, but maybe it trusts me to also know what I’m doing? Notify me of a pending auto-bolus so I can cancel it? Maybe someday.
Similar problems have hit me with Omnipod 5, poor or non existent insulin absorption causing nonsense numbers for IOB. (The Om5 algorithm works differently than Mobi and “fooling” it by going multiple days with poor absorption can screw up the algorithm for the following pod which seems to “learn” that the ones TDD increased a lot for no good reason…)
I have done various things to fix the problem, including:
Switch out the pod, using a new site;
Use my Manual basal mode with a temp basal increase for the next 4- plus hours or until I am solidly back in range. (Not sure if this option is available with Mobi but I hope it is)
Use Affrezza or syringe fast acting for immediate correction bolus to get back in range. (Causing a further delay until I guess that this “new” IOB is finished before confidently restarting the Automatic mode pump algorithm)
If I belatedly notice a bad infusion site and have let it screw up my IOB number on the pump for 1 plus days, I go back to manual basal and bolus on the next pod for “as long as it takes”, sometimes a half day or longer.
I know when this happens to me when I take the infusion set off there is usually a noticeable smell of alcohol. I think a lot of it ends up on the skin
I did not notice that at all. No smell, no moisture. Regardless, doesn’t IOB mean that the insulin is in your system?
It sounds like tunneling, where a channel is created that sends the insulin to just under the skin (intradermal injection) or to actually spill out on the skin.
If you see a bubble of skin when you remove the set, that could be a bleb, an insulin filled space. Otherwise you may notice the odor and feel of insulin on the skin.
If this continues to be a problem, contact Tandem support. You may need to use a set like TruSteel or another type with the teflon cannula.
Just got off a call with Tandem. Apparently even with a bent cannula, some insulin is delivered as long as pressure in the system is below 30 psi. If it goes above that, then an occlusion alarm sounds.
I didn’t notice that last night but I did when I got up this morning. It must all be eventually absorbed into your system tho’ as I woke up this am with BS level of 106 and almost no IOB
IOB in the software means the insulin was pumped out by the pump, and then the software calculates how much of it is still active by looking at the length of time since it was pumped out. The IOB number often will include insulin that never got absorbed for various reasons, most commonly (for me) a cannula that jiggled or was bumped and developed a little leakage at the site. When that happens it’s impossible to know what your IOB actually is, because you don’t know how much leaked out vs how much got absorbed in.
The occlusion alarm is the Achilles heel of my Tandem Tslim pump. It just does not work, even with the sensitive setting on. I never depend on it. So I would not trust the Mobi to alarm either.
The smell of insulin is not alcohol. It is a preservative that smells like formaldehyde and is very distinctive. As @RachelMaraii said, you can feel the patch sometimes and sniff your fingers to see if the canula has been tunneling insulin back to the skin
The insulin on board corrects itself in a couple of hours, so can be ignored for that time. I just bolus to correct the high number and watch to see if it turns out to be too much and I have to stuff myself with luscious carbs.
No, it might not be in your system. The pump knows that it successfully pushed the insulin out of the cartridge, that’s all. Who knows where the insulin actually went? Leaked out beside the cannula? Collected under the skin but not absorbed? These are failure modes, not all that common, but the pump has no way to know that the insulin it pushed out never actually made it into your bloodstream. In cases like this I take insulin via syringe to cover my guess as to the amount I needed that wasn’t actually in my system.
